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The VLTI view of compact dusty environments around evolved stars

Olivier CHESNEAU Observatoire de la Côte d’Azur (OCA). The VLTI view of compact dusty environments around evolved stars. The VLTI is at the moment in a ‘discovery’ stage, in the sense that many of the current studies have never been carried out by any optical interferometer.

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The VLTI view of compact dusty environments around evolved stars

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  1. Olivier CHESNEAU Observatoire de la Côte d’Azur (OCA) The VLTI view of compact dusty environments around evolved stars

  2. The VLTI is at the moment in a ‘discovery’ stage, in the sense that many of the current studies have never been carried out by any optical interferometer. • As a consequence, the current studies presented in this talk represent more an investigation of the possibilities of the VLTI than a focused research. • The evolved stars cover a zoo of phenomena that are interesting as they provide some information of the interior and environments of stars. Due to the multiplicity of the phenomena, there is also a zoo of spectral type… • The outline of the talk is the following: • Disk ‘hunting’ in the core of Planetary Nebulae (PNs) • Searching whether disks can have helped to shape PNs, • Searching, through the disks, the shaping agents, • The dust formation in evolved stars, • Searching how dust can form efficiently in these stars • Searching the origin of the asymetries suspected, • The Novae • Trying to detect asymetries close in space and time to the outburst, • Searching how dust form efficiently in dust forming event, • The Massive stars: disks around B supergiants, wind-wind collision in evolved massive systems, study of massive Wolf-Rayet stars…

  3. Thinking in Fourier space: 1 baseline = 1 visibility measurement per l • Possible approaches: • Do the 2-D fourier transform (not so intuitive), find the point corresponding to the baseline direction and length • In either case, decide on a baseline direction and length, then take the image and collapse it onto an axis in that direction. THEN take the 1-D Fourier transform! (more intuitive!)

  4. AMBER FOV with ATs 300mas MIDI FOV with UTs 300mas MIDI FOV with ATs 1300mas AMBER FOV with UTs 60mas Interferometric Field-Of-View

  5. Evolution of a low mass star AGB star (Leao et al., 2005 ) Adapted from Lattanzio & Boothroyd (1997) (evolution of a 1 Solar mass star)

  6. Different PNe Study of the envelopes of AGB and post-AGB stars 20” AGB star

  7. The hunting of disks in the center of Planetary Nebulae Context: the complexity of the shapes of Planetary Nebulae witness the many physical processes that can affect the outer regions of evolved giant stars as they follow the AGB/post-AGB/PN track. Emerging magnetic fields? Binarity (taking into account Jovian-size planets)? Nearly all models have now in common the need of a compact disk: The disk(s) are either circum-stellar or –binary. MIDI is an ideal tool for that (with complementary observations from HST, NACO adaptive optics, VISIR mid-IR images et VLTI/AMBER near-IR interferometry) Core Team: O. Chesneau, E. Lagadec, F. Lykou, M. Matsuura, A. Zijlstra, S. Wolf 5 systems already studied: 4 resolved with MIDI, 1 over-resolved (direct UT imaging) Lagadec, Chesneau et al. 2006, Matsuura, Chesneau et al. 2006, Chesneau, Collioud et al. 2006, Chesneau, Lykou et al. 2007

  8. The AMBER and MIDI instruments AMBER MIDI Near-IR (JHK) 3 telescopes Visibility, differential phase and phase closure R=30, 1500, 12000 θmin=2mas, beam=60mas Mid-IR (8-13μm) 2 telescopes Visibility and differential phase R=30, 230 θmin=10mas, beam=300mas

  9. CPD –568032 seen at different spatial scales 10 mm simulation 0.1 arcsec MIDI 8.7 mm image 1 arcsec 12 arcsec HST Chesneau, O., Collioud, A., De Marco O. et al., 2006, A&A

  10. MIDI data on CPD-56°8032 CPD1 B=45.7 m PA = -5° CPD2 B=45.6 m PA = 5° CPD3 B=41.2 m PA = 51° N CPD2 CPD1 Résolution36 mas à 8 µm60 mas à 13.5 µm CPD3

  11. Best geometrical model for CPD-56°8032 ? CPD1 B=45.7 m PA = -5° R = 72 +/- 3 mas(110 +/- 5 UA) N i = 29 +/- 5° CPD2 B=45.6 m PA = 5° E CPD3 B=41.2 m PA = 51° -15 +/- 5° Good model ???

  12. Best model 10 micron image Résolution : 13 mas par pixel SED fit based on carbon chemistry only Passive disk model

  13. Difficulties encountered • Dusty structure optically thin: projection effects, and inclination not constrained muchComplex geometry, an image is required, not only visibilities • Extended objectlink for low frequencies mandatory NACO/deep VISIR high spatial resolution (50-100mas) imaging required! Lessons learned • These sources are close to be resolved at 50-300mas scale, • High spatial resolution complementary techniques are absolutely required, to encompass the complexity of the source: NACO, VISIR (and HST), and avoid to over-resolve the source by the VLTI • We have to concentrate on ‘simpler targets’ for which the inclination (at least) is better constrained: i=0° PNs, or i=90° strongly asymmetric bipolar nebulae • Based on the work from Smith et al. 2003, 2005, we have chosen two well known targets:

  14. The bipolar PNs Mz3 and M2-9 • Central Stars • Not observable, • Bright core, many emission lines, unresolved at 0.1” scale • Nebula [Santander-Garcia et al. 2004, Guerrero et al. 2007, Schwartz et al.] • Bipolar with very narrow waist, • Strong IR emission  dust, in core and in lobes • SED similar in flux and shape, • Distance: ~1.5 kpc (but large range…) Menzel 3 (Mz3) The Ant M2-9 The Butterfly

  15. VISIR 12.8mm [NeII] An amorphous silicate disc in the Ant nebula, Mz 3 Chesneau, O., Lykou, F. et al., 2007, A&A MIDI visibilities for different baselines orientations HST observations

  16. 140 mas - 100 AU Density (2d disk)with α = 2.4 β = 1.03 h100AU = 17 AU VERY GOOD FIT, VISIBILITY+SED β = 1.03 α = 2.4 h(100 UA)=17 UA Rin = 9 AU 500 AU

  17. Which scenario for the formation of Menzel 3? • We have: • A large amount of dust in lobes (~solar mass, age ~1000yr), • A disk that represents only 1% of this mass, • The disk is formed of amorphous silicate  young, • Well defined limites for the lobes (shadowing effec!), • Most probably a binary system, including a star with initial mass larger than the sun • Hypothesis: • Formation of the lobes in one short (1yr?) event, the disk being a by-product of the event, • The event may have a ‘single-star’ origin (fast rotation/magnetism…) • Or may result from a ‘catastrophic’ interaction between the primary is fast expansion and the companion (no common envelope phase) • CAUTION: I do not mean that the case of Mz3 can be generalized! Chesneau, O., Lykou, F. et al., 2007, A&A

  18. The light-house effect of M2-9, the Butterfly http://antwrp.gsfc.nasa.gov/apod/ap070618.html

  19. Crystallinity! MIDI obs. to be continued… PdB proposal submitted A long-lived silicate disc in M2-9? B=40-60 m Soker & Livio (2001) WORK IN PROGRESS! (F. Lykou et al.)

  20. WD MIRA B Symbiotic Nova : 17–11 mag (~6months) The symbiotic system HM Sge • HM Sge : • Dusty symbiotic system (d~1.5 kpc), large separation 40mas~60 AU (Sources isolated with HST, Eyres et al. 2001) • Nova-like explosion (1975), unknown system before • Cold component: pulsating Mira (3000 K) + Hot component: White Dwarf (2105 K) HST: Eyres et al.

  21. HWHM~8 mas at 8.5mm (~12AU), flattening 0.8, Major axis perpandicular to binary orientation HWHM~13 mas at 13.5mm (~22AU), flattening ~1 Mira distorted wind or wind-wind collision? Imaging+high dynamical range needed (VLTI second generation+extreme AO) 3.5mas Teff=3000K Tin=1600K 10 = 2.5 N E U3-U4(~100°) E0-G0(~75°) U2-U3(~45°) MIDI Observations with UTs/ATs: 6 bases Various DUSTY models from literature tested, Double shell models discarded (Schild et al. 2000, Bogdanov & Taranova 2001) Sacuto, S., Chesneau, O., Vannier, M., et Crusalèbes, P. 2007, A&A, 465, 469

  22. IR interferometry of Mira stars Mira variables: Large variability amplitude ~ 9 mag (in V) Expanding dust shell Outer atmosphere (‘MolSphere’ Molecular layers, 2—5 Rstar ISO & high-resolution spectroscopy, Spatially unresolved Dust formation Photosphere Spectro-interferometry Spatial + Spectral resolution Near-infrared (JHK) Mid-infrared (N band) AMBER MIDI From K. Ohnaka

  23. Numerous papers from K. Ohnaka, M. Wittkowski and collaborators. Ohnaka, K., Driebe, T., Weigelt, G., & Wittkowski, M. 2007, A&A, 466, 1099 Wittkowski, M., Boboltz, D.A., Ohnaka, K., et al. 2007, A&A, 470, 191 Sacuto, S., Jorissen, A., Crusalèbes, P. et al. 2008, A&A

  24. The R CrBs (Asplund 1997) (Clayton 1996) • Very evolved objects : • No Hydrogene left, • Post-AGB at the end of the Helium burnig? • Resulting of the fusion of two White dwarves ? • Seem closely related to the born-again phenomenon (Clayton et al. 1996, 2001, 2007) Typical light curve resulting from the light absorbtion of dust clouds passing in the line-of-sight(Loreta 1934).

  25. Leao, I., De Laverny, P. et al. 2007, A&A VLTI monitoring of clumps formation and evolution but the wind itself is highly variable! Sphericity to be checked…

  26. Red supergiants Galactic ones, prototype Betelgeuse. Taking into account dust and molsphere Perrin, G., Verhoelst, T. et al. 2007 And now in the Magellanic Clouds!!! W04 supergiant, Ohnaka et al. 2008

  27. Origin of silicate carbon stars: AGB star + main sequence star (or white dwarf) • AGB, primary star: oxygen-rich, mass loss • Circumbinary disk is formed (Morris 1987; Lloyd-Evans 1990) Oxygen-rich dust (silicate) O-rich C-rich Mass loss Primary star becomes a carbon star. Oxygen-rich dust is stored in the disk  Silicate carbon star No theoretical or observational confirmation High-resolution observation in the silicate emission feature is the most direct approach  VLTI/MIDI Numerous papers from K. Ohnaka, P. Deroo and collaborators.

  28. What is the distance of the source? Is the ejection spherical? How a jet can form? How dust can form? Is the nova wind spherical?

  29. AMBER Observations of the recurrent nova RS Oph 5.5 days after discovery • One of the best AMBER dataset ever obtained BUT lonely data (1 triplet of base, 3 visibility curves and phase, one closure phase, • Competition: many optical interferometer observed it (PTI, Keck, IOTA) • Difficulty to understand a complex, evolving object for which most of the information comes from radio and X-rays, • We had to wait long, work hard to understand, with the pressure to publish fast (the ‘nova world’) • It was a good and hard first try for the VLTI! • Recurrent Nova: previous outbursts 1898, (1907), 1933, 1958, 1967, 1985 • Central system: high mass WD (1.2-1.4 M¤)+Red Giant (M2III); p = 455 d • The WD is claimed to be future progenitor of a supernova Ia Chesneau, Nardetto, Millour et al. A&A 2007, special issue on AMBER instrument

  30. Continuum K: 3.0 x 4.9 mas P.A. = 142° Brg 2.17 mm: 4.7 x 7.5 mas P.A. = 140° HeI 2.06 mm: 5.0 x 9.5 mas P.A. = 140°

  31. The asymmetric outburst of the recurrent nova RS Oph Radio obs. at t=13 days O’Brien et al., Nature, 2007 40 mas 65 AU Radio obs. at t=22 days 240 mas 380 AU HST visible image at t=150 days (Bode et al., ApJ, 2007) Chesneau, O., Nardetto, Millour et al., 2007, A&A • A very complex event! Main question: • What is the origin of the asymetry? • An asymetrical outburst (fast rotation)? • The influence of a preexisting disk, • Small amount of dust detected with Spitzer

  32. First observations, K=3.3 Second observations, K=4.5 H=2.9, near-IR C lines End of PTI obs. (14), K~6.5 H=3.7 DDT submitted Rapid end of outburst 10 days Strong dust formation event One year The dust formation event of V1280 Sco monitored by MIDI and AMBER RS Oph was a reccurrent nova: this implies many earlier studies! ‘Simple’ light curve in visual and in K band… Then, one year later V1280 Sco came: one of the brightest nova observed these last 35 years… VLTI DDT proposal on AMBER proposed, and accepted, but things got complicated…

  33. K H V

  34. Classical result: a distance estimate… A ‘dusty’ distance estimation • ….BUT…. • Based on the expansion of a dust shell…~0.35mas/d • Taking into account a radial velocity from IAU notices… • 500km/s (relatively slow…) • and a crude error estimate +/-100km/s • D~ 1.6+/-0.4kpc… • The nova was not so close…but the outburst was MASSIVE. Chesneau, O.et al., 2008, A&A, in preparation

  35. 13th March, t=36d, 13mas 23rd March, t=46d, 16mas Good temporal coverage, good data quality BUT ALMOST NO UV COVERAGE! ALMOST NO INFORMATION ON GEOMETRY! Sphericity assumed in absence of obvious sign of departure 6th May, t=90d, 26mas

  36. 23th Mar.2007, day 46 28th Feb.2007, day 23 13th Mar.2007, day 36 26th May.2007, day 110 30th June.2007, day 145 6th May.2007, day 90 Chesneau, O., Banerjee, D., Millour F., Nardetto N.et al., 2008, A&A, in press

  37. A full set of models for each date of observation T pseudo- photosphere T inner radius Dust mass estimate Knowing that the nova emerged from its dusty cocoon in November 2007 only (~250d after discovery), we easily can estimate the ejected mass to 10-4 solar mass: one of the heaviest event ever recorded Care! This does not imply that the WD was massive! The hydrogene stolen from the companion slowly stratified. If the WD is ‘small’ (0.6 solar mass), a large mass is needed to reach the temperature and pressure level for the ignition of the nuclear reactions!.

  38. Lamers et Cassinelli, 1999 Mass loss from evolved stars: loss of spherical sphericity Massive stars (‘Hot’) Associated issues: . Binarity, . Rotation, . X ray generation in radiative winds, . Supergiant eruptions and instabilities, . Supernovae Ib,c, II remanent geometry . Dust production from hot stars . LBVs, . B[e], . WR of carbon type,

  39. Weigelt et al. 2007 Fast rotation and now… The hunt of the companion!

  40. AMBER FOV with ATs 300mas MIDI FOV with UTs 300mas MIDI FOV with ATs 1300mas AMBER FOV with UTs 60mas Interferometric Field-Of-View

  41. Rotation? Binarity? Complex evolution? The B[e] phenomenon(Lamers et al. 1998) Supergiants B[e]  L*/Lsun > 104 Observations point towards asymmetrical stellar environments Zickgraf et al. (1985)

  42. (A. Meilland) long axe short axe Domiciano de Souza et al. (2007 A&A ; ESO Press Release 2005) CPD-57 2874 VLTI/MIDI VLTI/AMBER

  43. HD 87643: a Sg B[e] LBV MIDI 2pts LBV MIDI 1pt B[e] MIDI/AMBER LBV MIDI/1pt, non rés. CPD MIDI? CPD B[e] MIDI/AMBER GG B[e] MIDI/AMBER CD B[e] à observer HD LBV à observer? BI Cru? B[e] HaBe Eta Car… McGregor et al. 1988

  44. MIDI GTO data: a mess… Is the image of the source achromatic? A disk model does not work… Surprisingly, a double ring model fits in…

  45. V Spatial Frequency New AMBER data requested… Run ID Telescope Instrument Hours 380.D-0340(A) VLTI AMBER 4.5 B 380.D-0340(B) VLTI AMBER 4.5 C NACO DDT observations accepted (and performed, waiting for the data) HD 87643 is a binary!!! Probably B+B system! +disk,+jet+???? Paper in preparation: Millour, Chesneau et al. 2009

  46. March 2007 Jan 2007 Nov 2006 Radiation hydrodynamics simulation of CIRs in a hot-star wind • These may stem from large-scale surface structure that induces spiral wind variation analogous to solar Corotating Interaction Regions. Rigel (b Orionis): B8Ia

  47. The asymmetric environment of evolved stars • So far, the study of asymetric environments is very rich, we discover the potential: • The core of PPN/PNs (a team is formed, currently limited to ~10 sources), • Nova observations (an international collaboration is under way, 2 novae per yr), • Study of large dust clumps, (many sources, a team is slowly forming) • Study of ‘mol-spheres’ and pulsating stars (many sources, a well-identified team) • Symbiotic systems with dust: complex geometries suspected, high dynamics needed (Almost no dedicated study to date, except for binary post-AGBs) • Evolved B supergiants with dust (a growing team is formed), • Wind activities in OB stars, wind-wind collision zones (no organized team yet, but some focused collaborations) • My strategy with the VLTI: reassess famous, ‘prototypal’ targets, demonstrate the possibilities of the instrument. The VLTI observations and interpretation of evolved stars are to date manpower limited, not instrument limited. A number of 10-20 papers in the field of evolved stars could be published from the observations per year, in an ‘industrial’ sense. In depth, more systematical studies must come later. These studies are an exploration of the possibilities offered by the VLTI A great VLTI2/ALMA synergy expected in a few years, Large scale studies will become possible (manpower needed!)

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